Johnson 120 V4 Looper

[kgilly22]

I have a 86 Johnson 120 V4 Looper. Took it out today and it fired right up. Idled fine through the no wake zone and took off no problem. Ran great wide open for about one minute then just died. Restarted and it had a hard time getting planed out again but once it did it ran wide open for about 45 seconds and died. Did the same thing one more time and then would hardly start and run for more than a few seconds. The carbs were rebuilt two summers ago but it has sit in the shed quite a bit since then. Running sea foam with the fuel. I am just wondering if anyone has any ideas. Any help would be appreciated.

 

[HighTrim]

Re: Johnson 120 V4 Looper

Start by checking the spark and compression. Basics first. Ensure it is firing on all cylinders and the compression is adequate. Should throw a strong blue spark over 1/2 inch and be within 10 percent compression on all cylinders.

Let us know what you find

 

[Brew2]

Re: Johnson 120 V4 Looper

I'd start by having a look at the carbs as fuel delivery issues certainly sound like probably cause....running seaform in gas is ok, but no substitute for taking off the carbs and giving them a good cleaning with some aerosol carb cleaner then following up with some compressed air through the carb passages. Could also look for air leaks or kinks/restrictions in the fuel lines...both the main fuel line and the smaller ones leading to the carbs.

Have you tested the overheat warning alarm? Find the tan wire leading to the cylinder head, peel back the black rubber sleeve that covers the sissor connection point (should be a couple of inches from the cylinder head), then with the key in the on position, ground the end of the wire leading to the front of the boat on the engine block....the alarm should sound....if not, then you may have overheated the motor and not realized it.

Post back with what you find out.

Good luck!

 

[kenmyfam]

Re: Johnson 120 V4 Looper

Did you try pumping the fuel bulb while it wanted to give out ???

 

[kgilly22]

Re: Johnson 120 V4 Looper

Thanks for the replies everyone. I will not have a chance to look at it further until this weekend but I did try pumping the primer bulb when it was giving out with no luck. Also tried bumping the choke to see if it would pick up but nothing there either. I will let you know what I find out this weekend. Thanks again.